1. Field of the Invention
The present invention relates to a method for electrolytically etching a ferrite body wherein the body is employed as the cathode in an electrolytic cell under controlled conditions to secure the required etching.
2. Description of the Prior Art
In the manufacture of ferrite magnetic transducer heads, for example, it is necessary that the ferrite starting material which forms the head cores be provided with grooves. One system commonly employed consists in grinding grooves into a pair of ferrite blocks and then adhesively bonding the blocks together. In such mechanical processing, however, the dimensional accuracy is not sufficiently great. This is particularly true in the case of manufacturing a video magnetic head which requires a high degree of accuracy. Consequently, it is difficult to produce magnetic heads which have uniform characteristics economically. Furthermore, in the case of mechanical processing, defects such as residual distortion in the head are created, and the magnetic characteristics of the ferrite are deteriorated. In addition, in the case of mechanical processing, the magnetic head which can be produced is limited in terms of its configuration.
Another technique which has been used is the chemical etching technique. In this type of technique, a highly concentrated acid such as a 50% aqueous solution of hydrochloric acid or concentrated phosphoric acid is used. When phosphoric acid is employed, it is heated up to about 50.degree. C. to make the etching speed sufficiently high.
In the typical chemical etching technique, an etching resist is coated on the ferrite body, and a suitable pattern is photographically applied to the resist coating, and selectively removed by development to provide a patterned ferrite body. Then, this body is etched with the acid in the portions of the resist coating which have been removed by the development process. With this type of chemical etching, however, there is a substantial amount of undercutting or side etching because the etchant permeates into the ferrite block beneath the resist coating and beyond the limits of the desired pattern. It is accordingly difficult to form a deep groove in a ferrite body by means of the chemical etching technique.